There exist in today's market scanning devices capable of reading ID cards, drivers license, business cards and the like. Scanning devices which include imaging sensors based on technologies such as a CCD or CMOS, require illumination of the scanned document.
Illumination coming from external sources such as room illumination often creates uncontrolled reflections on the scanned document, thereby distorting the image of the scanned document. Internal light sources may also bring about problems of reflections that distort the uniformity of the illumination of the scanned document, thereby causing the image of the scanned document not to be a substantially true image of the scanned document.
Reference is made to FIGS. 1a (Prior art) and 1b (Prior art). FIG. 1b depicts a hot spot 40 caused by direct illumination of the scanned document 10 or by illumination from external source entering the scanned from bare areas of the scanner glass window, and FIG. 1a illustrates how hot spots 40 are formed by direct illumination of the scanned document 10 or glass window 20 in front of the scanned document. When imaging a document 10 with a camera 50, document 10 needs to be illuminated. In conventional illumination method, as shown in FIG. 1a, illumination positions 31 and 32 enable the return of the majority of light to the lens of camera 50, but give rise to a problem known in the art as hot spot 40, where the light source (30) itself is imaged by camera 50.
Thus there is a need for and it would be advantageous to have a camera based scanner that has an illumination system that provides uniform illumination with no reflections, hot spot effects, and other illumination artifacts.